The present invention relates to a tool and method for facilitating communication between a computer apparatus and a device in, on or near a drill string, particularly, but not exclusively while tripping drill pipe.
In the drilling of a borehole in the construction of an oil or gas well, a drill bit is arranged at a lower end of a drill string, which is rotated to bore the borehole through a formation. A drilling fluid known as “drilling mud” is pumped through the drill string to the drill bit to lubricate the drill bit and returns carrying drill cuttings in an annulus between an outer wall of the drill string and the borehole. As the drill bit progresses through the formation, stands of drill pipe are added to the drill string. Stands of drill pipe typically comprise two, three or four joints of drill pipe threadedly connected together in a mousehole in a drilling rig floor using an iron roughneck and set back in a fingerboard pipe rack. A joint of drill pipe is typically 31 ft 6 inches long (9.65 m). Each joint of drill pipe has a hollow cylindrical body with a lower threaded pin end and an upper threaded box end. As the drill bit progresses in the borehole, the drill string moves downwardly. When an upper end of the drill string nears the rig floor, a stand is pulled out of the fingerboard pipe rack. The top of the stand is placed in an elevator, and the lower end aligned with a top of the drill string at well centre. A lower threaded pin end of the stand of drill pipe is stabbed into an upper box of the drill string and threadedly connected using the iron roughneck. Drilling then continues using rotation of a top drive, a rotary table or downhole motor. The drill string can be many hundreds or thousands of metres long.
The drill string may be pulled out of the borehole for many reasons, such as: to change the drill bit; to allow for a string of casing to be lowered into the borehole for casing the borehole; to hang a liner; to set a whipstock for deviated drilling; to lower milling tools; to fish for stuck tools; to clean the borehole; and prepare the borehole for production. The step of pulling the drill string out of the borehole is known as “tripping-out” and the step of lowering the drill string back into the borehole is known as “tripping-in”. During tripping, the string of drill pipe is not rotated or only rotated slowly in order to facilitate a smooth movement along a borehole, which may be deviated or partly horizontal.
As will be appreciated, as the drill string is pulled out of the borehole, a stand of drill pipe is disconnected using an iron roughneck and the stand placed back into the fingerboard pipe rack, usually using a pipe handling tool, such as a racker.
It is important to receive information from a multiplicity of downhole devices, such as downhole tools and sensors. Some examples are Measuring Whilst Drilling tools (MWD) and Logging Whilst Drilling tools (LWD) which are located in the Bottom Hole Assembly. Further data, such as temperature and pressure readings may be obtained from further sensors arranged on the Bottom Hole Assembly and along the length of the drill string. Generally, the more data that can be obtained from downhole, the greater the chances of constructing a successful well. Such modern tools and sensors create a lot of data. This data can be stored in a local data storage device, such as on a Random Access Memory (RAM) chip within the tool in the Bottom Hole Assembly, and physically brought back to the surface with the BHA in a trip. The RAM chip is physically plugged into a computer at the surface to obtain the data. Alternatively, the information can be accessed whilst the BHA remains at the bottom of the borehole. This can be achieved using wires which run along each joint of drill pipe, with special connectors provided to provide continuity of connection between each joint in the drill string. Such wired communication is provided by Intelliserv, a subsidiary of National Oilwell Varco. Thus information from downhole can be obtained in real time. The wired connection can also send instructions downhole to control downhole tools, measuring devices and sensors. Information may be sent along such a wired string during drilling using an Instrumented internal Blow Out Preventer (IIBOP), such as the IIBOP provided by National Oilwell Varco under the trade name String Sense™. The IIBOP provided with an upper box end, a lower pin end and a selectively open flow path there between, as with a standard Internal Blow Out Preventer. The upper box end is threadedly attached to a Main rotating shaft of the top drive, immediately below the top drive. The lower pin end is threadedly connected to a wired sub. The wired sub provides a continuous wired connection to the IIBOP when threadedly connected with the string of drill pipe in the borehole. A communication path is established across the String Sense™ IIBOP to a rotary connection, which transfers data to a rotationally stationary wire or wire bundle which is draped over the top drive and into a travelling loom to a computer in a driller's cabin, known as a dog house, on the drilling rig.